Chapter 2 The Chemistry of Life

Chapter Outline Section 1: The Nature of Matter Section 2: Water and Solutions Section 3: Chemistry of Cells Section 4: Energy and Chemical Reactions

Section 2.1 Nature of Matter Why look at chemistry in a biology class? All living organisms have chemical “machinery” 2.1 Covers: Atoms, Elements, Chemical Bonding

Atoms Atom is the smallest unit of matter that cannot be broken down by chemical means Very small and always changing 3 particles make up an atom Electrons (-) Protons (+) Neutrons (neutral) Attract each other… *Therefore atom itself has no charge (negative electron cancels out positive proton)

Atomic Structure Electron Cloud made of electrons (-) Nucleus made up of protons (+) and neutrons (neutral), nucleus has a (+) charge

Element An element is a pure substance made of only one kind of atom Represented by chemical symbols (C, N, H) Elements have different atomic numbers (C=6, O=8) Atomic number = # of protons

Differences in Elements Atomic Number all atoms of a particular element have the same number of protons which is called the atomic number. Ex: Helium = 2 b/c it has 2 protons

Isotopes Different number of neutrons than protons Carbon 12, 13, 14 6 Protons in each but Carbon 13 has 7 neutrons and carbon 14 has 8 neutrons

Energy Levels

Chemical Bonding Atoms can join together to form a stable substance The force that joins atoms together is called a chemical bond A compound is a substance made of 2 or more elements. 3 Types of Bonds Covalent Hydrogen Ionic

Arrangement of electrons determine how atoms bond together Electron levels Closest to nucleus = 2 electrons Second level = 8 electrons Atom becomes stable when the outer electron level is full

Covalent bonds Hydrogen =H has only 1 electron in its outer most level Form when 2+ atoms share electrons to form a molecule. Hydrogen =H has only 1 electron in its outer most level Oxygen =O has only 6 electrons in its outer most level They react to fill each ones outer most level 2 2 2 3 1 6 4 5

Ionic Bonding Atoms gain or lose an electron, causing them to be charged. They become charged because they contain an unequal number of electrons and protons

Gaining/Loosing an Electron Gaining an electron makes the atom negative You have more electrons (-) than protons (+) Loosing an electron makes the atom positive You have more protons (+) than electrons (-)

Ionic Bond Example Na LOST an e- so it became more positive Cl GAINED an e- so it became more negative

Hydrogen bonds Electrons more strongly attracted to the oxygen nucleus than by the hydrogen’s This unequal distribution of electrical charge are called polar molecules Partially positive end of one molecule is attracted to the partially negative end of another

Polar Molecule (Water) Which pole attracts which pole?

Exit Ticket Draw a carbon atom (Atomic number = 6) Label all the parts and correctly show the number of electrons in the right levels Write 3 things you learned today

Begin 2.1 Section Review Page 30 Questions 1-4 Finish for HW

Chapter 2 Section 2 Water and Solutions

Water in Living Things 70% of your body is made of water Water helps move nutrients and other substances into and out of your cells Certain properties of water make it such an important substance for life Storage of heat Cohesion & Adhesion

Storage of Heat Water heats more slowly and retains heat longer than many other substances Many organisms release heat through water evaporation Sweating Helps maintain homeostasis

Cohesion & Adhesion The hydrogen bonds between water molecules cause the cohesion of liquid water Cohesion Attraction between substances of the same kind Surface tension prevents water from breaking easily Adhesion Attraction between substances of a different kind Substances get wet Capillary action water molecules move up through a narrow tube (stem of plant) Because of these water can move up the stems of leaves

Aqueous Solutions Many substances dissolve in water Solution is: a mixture in which one or more substances are evenly distributed in another substance. Because certain substances can dissolve in water they can more easily move throughout the body

Polarity Enables many substances to dissolve in water When ionic compounds are dissolved in water, the ions become surrounded by polar water molecules Ions and molecules become evenly distributed in the water Non polar molecules do not dissolve in water well (oils)

Acids and Bases Pure water always has a even concentration of hydrogen ions (H+) and hydroxide ions (OH-) Acids have a higher concentration of hydrogen ions. Bases have a higher concentration of hydroxide ions.

pH Scale

2.3 Chemistry of Cells Most matter in your body that isn’t water IS an organic molecule Organic = Carbon based 4 classes of organic molecules in your body (can’t function w/o them) Carbohydrates Lipids Proteins Nucleic Acids

Carbohydrates Organic molecules made of carbon, hydrogen and oxygen Major source of energy for the body Found in most foods (fruits, veggies, grain) in the form of sugars 3 types of sugars Monosaccharide (1 sugar unit) Disaccharide (2 sugar units) Polysaccharide ( 3+ sugar units) Macromolecule large molecule made of many smaller

Examples of Sugars (Carbs) Polysaccharides storehouses for energy starch, glycogen, cellulose Starch – made by plants Glycogen- made by animals Both made from linked glucose molecules (pg 34) Cellulose- made by plants (for structure)

Lipids Non-polar molecules… soluble or non-soluble? Fats, phospholipids, steroids and waxes Steroids (cholesterol, estrogen, testosterone) Important for structure and function of cell membranes Lipids store energy

Structure 3 fatty acids bonded to a glycerol molecule backbone (pg 35) Fatty acid is long chain of carbon atoms with hydrogen bonded to them Strong bonds between carbon and hydrogen  can store lots of energy

Saturated and Unsaturated All carbons are bonded to 2+ hydrogen Most animal fats Butter, lard, grease Usually solids at room temperature Unsaturated Some carbons linked by a double covalent bond Causes kinks in chain Plant oils, olive oil, fish oils Liquids at room temperature

Unsaturated Fats

Proteins Large molecules formed by linked smaller molecules called amino acids (AA) AA are building blocks of proteins Only 20 AA Cause various shapes of proteins Some proteins are enzymes (help chemical reactions) Others used for structure Skin, ligaments, bone (Collagen) Hair & nails (keratin) Muscle (myoglobin) Blood (hemoglobin)

Example of a Protein??? Enzymes! Lower the amount of energy needed to start the reaction without changing the original reactants. Reaction runs faster!

Energy Chemical Reaction Reactant 1 Products + Reactant 2 Hydrogen Oxygen water

Enzymes Shape specific - Fits like puzzle piece Active site Each enzyme has its own specific substrate (reactant)

Enzymes What affects enzymes? pH, temperature, environment

Collagen Hemoglobin

Nucleic Acids All cells contain nucleic acids (in all cells) Long chain of smaller molecules (nucleotides) 3 parts Sugar Base Phosphate group (P& O) 2 types of nuclei acids DNA- deoxyribonucleic acid RNA- ribonucleic acid

DNA 2 strands of nucleotides that spiral around each other Chromosomes contain long strands of DNA (stores heredity)

RNA Single strand of nucleotides Key roles in protein synthesis Acts as enzyme  helping chemical reactions link AA to form proteins